Change to format string; does autoblack work?

Author: rocky

mathicsscript/version.py

@@ -3,4 +3,5 @@
 # This file is suitable for sourcing inside POSIX shell as
 # well as importing into Python. That's why there is no
 # space around "=" below.
+# fmt: off
 __version__="3.1.1.dev0"  # noqa

rst2html.py

@@ -51,7 +51,7 @@ def clean_line(line):
             for (regex, sub) in regex_subs:
                 line = regex.sub(sub, line)
         except Exception as ex:
-            print("ERROR: %s, (line(%s)" % (regex, sub))
+            print(f"ERROR: {regex}, (line({sub})")
             raise ex
 
         return line